Along with an increase in integration of semiconductor devices and an increase in fineness of patterns, a reduction in the resistance of a gate electrode has been desired. As a method for reducing the resistance of the gate electrode, a method of turning the gate electrode into a silicide by a SALICIDE (Self-Aligned Silicide) technique is known.
To form an ohmic contact by the work function of the interface between a metallic material for wiring and silicon in a silicon semiconductor, a method of modifying the surface of the silicon layer with other metal such as Co, Ni, Au, Ag, Ti, Pd or Al and a silicide or the like has been often used. Further, as the silicide, cobalt silicide has been often used in view of the specific resistance of the silicide itself and matching between the lattice parameters of the silicide and silicon (refer to U.S. Pat. No. 3,382,743).
These silicides are generally formed by a method comprising laminating a metal film such as Co, Ni, Au, Ag, Ti, Pd or Al on a silicon film by a vacuum process such as a vacuum deposition process, a sputtering process, a plasma CVD (Chemical Vapor Deposition) process, a thermal CVD process, an optical CVD process or an MOCVD (Metal Organic CVD) process and then treating the resulting film at high temperatures (refer to Jpn. J. Appl. Phys. Vol. 40, pp. 2,778 (2001) and Applied Physics, vol. 63, No. 11, pp. 1,093 (1994)).
However, these deposition methods have the following problems. That is, since they deposit silicon and cobalt in a gas phase regardless of physical deposition or chemical deposition, production costs are high due to a large-size apparatus, and it is difficult to form a coating film on a large-area substrate because particles and oxides are liable to be produced.
Further, since the deposition methods use a compound which becomes gaseous under vacuum regardless of physical deposition or chemical deposition, compounds that can be used as a raw material are limited, and highly sealed vacuum equipment is required. These also cause an increase in production costs.
Meanwhile, in various electric circuits, resistors are used for the purposes of voltage drop, voltage division and generation of module heat. In general, a number of resistors having various electric resistance values must be used according to their purposes, installation positions and the like. Therefore, electric circuits having such resistors cannot help having a certain size, thereby inhibiting a reduction in the size of electric equipment.
It is obvious that if a certain electric resistance can be imparted to a wiring material, many resistors in the circuit become unnecessary, thereby contributing to a reduction in the size of electric equipment. Although a silicon-cobalt alloy (cobalt silicide) is expected to be promising as such a wiring material, its formation requires a large-size apparatus as described above and therefore causes high costs. Hence, its use in this field has hardly been studied.
Under the above circumstances, an industrial film formation method of a silicon-cobalt film which requires no expensive vacuum equipment and high-frequency generator and does not require high production costs has been strongly desired.